It depends, the war aims changed throughout the war, generally based on how well the German armies were doing. In general the plans revolved around reducing the power of France and Russia. The great concern pre-war as the ability of those nations to act in concert and crush Germany in a vice. So the primary war aim was always to reduce their power.

Probably the best known "plan" was Bethmann-Holweg's proposed "Septemberprogramm." Here are some of the major points of the plan.

• In the West, Germany was going to either annex Belgium directly or at least make it into a protectorate client state. Parts of NE France would also be annexed to either Germany or to the Belgian client state. And Luxembourg would be forced to join the German empire as a constituent state. France was also going to have a large indemnity imposed on it.
• In the East they wanted pretty much exactly what they got from Brest-Livosk, a huge swath of territory including the Baltics, Poland, Belorussia, Ukraine, and the Caucuses. Like Belgium these would either be annexed and directly run by they empire; or they would be pulled into a tightly managed series of client states; probably similar to how the Warsaw Pact nations were managed by the Soviets.
• They also planned on creating a customs union and maybe a monetary union (sort of a proto EU) which would be dominated by Germany and run for Germany's benefit. Mainly this would include the newly created client countries, but other nations would also be heavily pressured to join.
• In Africa Germany was going to grab Belgian Congo and some French colonies. There were also hopes that they could buy or otherwise trade Angola from Portugal. Here the plan was to connect the existing German colonies, and create a super Central African German colony.